Just my 2 cents, but... why put all that power into one pc and not 2 or 4 separate ones?
Build a little render farm. That way you can get away with smaller PSUs, 4 "normal" ones probably being cheaper as 1 really big one or 2 big ones - especially when you need to replace one.
Also as a bonus you get redundancy. If one blows you have 1 to 3 renderers still running, not a complete fallout.
The hardware besides the PSU could probably be extremely streamlined, if additional machines do nothing but render. Pretty cheap board/cpu/ram, GPUs you already have, maybe still a fast SSD for reading/writing data (or a small ssd-nas for having source and output files centralized - but then you'd have to invest a bit in the network. maybe going for 2.5gbit or even 10gbit).
As I said... just my 2 cents. And without knowing how 4 GPUs in one machine would even get separate jobs (was SLI still a thing with 3090s or would SLI even make sense there?) or what your renderer is and if separate software licenses would make this prohibitively expensive or whatever.
Build a little render farm. That way you can get away with smaller PSUs, 4 "normal" ones probably being cheaper as 1 really big one or 2 big ones - especially when you need to replace one.
Also as a bonus you get redundancy. If one blows you have 1 to 3 renderers still running, not a complete fallout.
The hardware besides the PSU could probably be extremely streamlined, if additional machines do nothing but render. Pretty cheap board/cpu/ram, GPUs you already have, maybe still a fast SSD for reading/writing data (or a small ssd-nas for having source and output files centralized - but then you'd have to invest a bit in the network. maybe going for 2.5gbit or even 10gbit).
As I said... just my 2 cents. And without knowing how 4 GPUs in one machine would even get separate jobs (was SLI still a thing with 3090s or would SLI even make sense there?) or what your renderer is and if separate software licenses would make this prohibitively expensive or whatever.